I. Field
The following description relates generally to wireless communications, and, amongst other things, to precoding and space division multiple access (SDMA) support for wireless communication systems.
II. Background
Wireless networking systems have become a prevalent means by which a large number of people worldwide communicate. Wireless communication devices have become smaller and more powerful to meet consumer needs, which include improved portability and convenience. Users have found many uses for wireless communication devices, such as cellular telephones, personal digital assistants (PDAs) and the like, and demand reliable service and expanded coverage areas.
Performance for a wireless communication system may be enhanced by using beam-formed transmissions within a region to communicate from a base station or access point to the mobile device(s). Such a region can be a service area and can include sub-regions, or sectors. Multiple transmit antennas located at the base station can be used to form beam-formed transmissions, which utilize “beams” that typically cover a narrower area than transmissions using a single transmit antenna. The signal to interference and noise ratio (SINR) is enhanced within the area or sector covered by the beams. The portions of the sector not covered by a beam are referred to as a null region. Mobile devices within this null region generally have an extremely low SINR, resulting in reduced performance and possible data loss. The communication system may use beam steering, in which beams are dynamically directed at particular user devices. During beam steering, beams are redirected as user device(s) change location.
A challenge in communication systems is that the mobile device or receiver is located in a specific portion of an area served by the access point or transmitter. In such cases, where a transmitter has multiple transmit antennas, the signals provided from each antenna need not be combined to provide maximum power at the receiver. In these cases, there may be problems with decoding of the signals received at the receiver.
To overcome the aforementioned, there is a need for techniques to improve the signal-to-noise (SNR) ratio of a wireless link with multiple antennas. The improved SNR can also improve decoding of the signals by the receiver.